Ninth-seed Sabalenka, who beat world number one Ashleigh Barty in semi-finals, needed to show plenty of character to recover and then see off the unseeded American 6-3 3-6 6-1 in a match which lasted almost two hours.
"I can't believe that I defend this title. I couldn't even imagine that I will be able to do this," the Belarusian, the world number 14, said on the WTA Tour website.
"Right now I'm just happy. I can't believe it's happened.
"This means a lot. This year been really tough for everyone."
At the Tashkent Open, third seed Alison Van Uytvanck defeated Sorana Cirstea in another final which went the distance.
The Belgian eventually won 6-2 4-6 6-4 in two hours and 24 minutes to claim her second WTA title of the season.
Saturday saw the start of the China Open in Beijing, where former French Open champion Jelena Ostapenko battled past second seed Karolina Pliskova.
The Latvian, given a wildcard entry, recorded a 7-5 3-6 7-5 win over the world number two in a match which lasted just under two-and-a-half hours.
Earlier, US Open semi-finalist Belinda Bencic booked her place in the second round with a straight-sets win over Hsieh Su-wei.
The ninth-seeded Swiss progressed 7-5 6-2 and will next face with Venus Williams or Barbora Strycova.
Dutch number eight seed Kiki Bertens came through 3-6 6-1 7-6 (3) against Croatian Donna Vekic, while there was home success as Zheng Saisai battled past Monica Puig 4-6 6-3 7-6 (5).
Saturday's late matches saw Sofia Kenin of the United States edge out Spain's Garbine Muguruza 6-0 2-6 6-2, while Russian Daria Kasatkina was a 2-6 6-4 6-4 winner over Chinese wildcard Peng Shuai.
